Maritime Communication: A Look at Modern and Traditional Methods

Back then, shipping was relatively slow regarding the use and application of technological developments. However, it was never the case when it comes to maritime communication.

From the time of flag semaphores used as the primary means of communication for ships to the rise of GMDSS, maritime communication has gone through a long and winding evolution through the years.

Maritime communication involves ship-to-shore interactions, including arrival contact notices with ports and voyage instructions and ship-to-ship interactions like the safety of navigation concerns. In these modern times of enhanced connectivity, it’s expected for shipping legislation to mandate information reporting and vessel communication.

Continue reading below to learn more about the traditional and modern methods of maritime communication:

Maritime Signal Flags

The use of maritime signal flags dates back to ancient times. The system uses a series of flags to spell out a particular message, with every flag representing a specific letter.

Each flag has a particular meaning. For instance, when a diving support vessel raises the A flag, it cannot move from its present location because a diver is underwater. It serves as a warning to the other vessels to stay clear. This is how maritime signal flags are considered the most effective means of sending messages, even without technology.

This principle system of maritime signal flags also comes with associated codes known as the International Code of Signals. This is an international system of principles and signals vessels use to communicate key messages, such as those related to navigational safety. It’s essential when there are existing language difficulties.

Radiotelephony, radiotelegraphy, flag semaphore, flag hoist, and signal lamp or blinkers are used for sending signals. The IMO currently maintains the Code that was published in the latest print edition back in 2005.

Radiotelegraphy

The Morse code and other similar coded signals allowed ship-to-shore communication via radio during the early 19^th century. The Morse code is the method where text characters are encoded as standardized sequences of two signal durations, dahs and dits.

The International Morse code encodes 26 basic letters in Latin from A to Z, the Arabic numerals, a small set of procedural signals and punctuation or prosigns, and a single accented Latin letter, É. But the fact that there is a need to individually transmit each letter soon made the technology obsolete as it only added to the expenses for vessel communication.

VHF

The introduction of VHF radio paved the way for a significant change in maritime communication. This made ship-to-ship communication a reality and enhanced the safety of all people involved.

With the use of FM channels in VHF or very high-frequency radio bands, two-way radio transceivers are involved in marine VHF radio on ships that enable voice communication, not just from ship-to-ship but ship-to-shore, with the help of harbor managers.

It was as early as the 1900s when marine VHF was implemented globally, not long after Guillermo Marconi invented radio technology. But with a frequency of less than 1GHz, it was also expected for VHF technology to come with some everyday challenges regarding radio limitations.

Satellites

To eliminate the challenges related to the use of VHF radio, all member nations were encouraged in 1979 by the IMO to establish MMSC or Maritime Mobile Satellite Communication systems. The satellite antenna has been a weak link to systems ashore as the enabler of modern maritime communications since the latter part of the 20^th century.

VSATs

The vast amounts of data generated by most satellite communication systems have long been a severe challenge for maritime communication. This is precisely what the tiny aperture terminal or VSAT hopes to address.

With a monthly subscription to VSAT services, operators are given exclusive use of satellite channels to send and receive data and avoid. This allows a network that makes the transmission of vast amounts of data possible.

GMDSS

During the early 1990s, a new era for maritime communication entered the picture with the introduction of GMDSS or the Global Maritime Distress and Safety System. GMDSS is an integrated communications system using terrestrial radio and satellite systems. It was on February 1, 1999, that GMDSS had its full implementation. It officially got rid of the Morse code as a method of maritime communication.

All cargo ships and passenger ships of more than 300 GT on global voyages are mandated by the SOLAS in Chapter IV to carry specific satellite and terrestrial radio communications equipment to send and receive maritime safety information and distress alerts. This is also mandated for general communications based on the IMO. The GMDSS also offered communication via email as an option that needed to be improved in the past.

It was in 2022 when the IMO approved the GMDSS’s modernization plan. The respective amendments are expected to be implemented by 2024.

Digital Selective Calling

DSC or Digital Selective Calling, is part of the GMDSS, allowing better communication capabilities. These included remote control commands to receive and transmit distress signals, put out routine messages, and place urgent safety calls.

The DSC controllers are often incorporated with the VHF radio as mandated by SOLAS. DSC was meant to replace the voice calls utilized in traditional procedures as it transmits predefined digital messages through the VHF.

Automatic Transmitter Identification System

The European inland waterways command the use of ATIS or Automatic Transmitter Identification System under the Basel agreement as a part of VHF radio. This conveys the vessel’s identity which comes in the form of a code of 10 digits after every voice transmission.

Existing Challenges in Maritime Communication

Due to the ever-increasing digitization of modern maritime communications, it’s almost expected that it also resulted in several cyber vulnerabilities. These require constant vigilance on the part of satellite communication operators and providers. It also prompted the IMO to recommend to ship operators in 2017 to address the concern in their SMS.